Steam reforming processes are known, and are used for converting various kinds of carbonaceous materials into useful commodities. The term carbonaceous material (“CM”) as used herein includes any carbonaceous material, including: municipal solid waste (“MSW”); industrial, commercial and institutional waste (“ICIW”); medical waste; coal; coal waste; wood waste; sawdust; forest product waste; agricultural waste; sewage; liquid waste; hazardous waste; waste oil and oil by-products; electronic waste and other similar carbonaceous substances; also included are opportunity materials such as incineration and/or combustion ash, which may be used in order to achieve conversion upgrade opportunities in existing incineration plants.
In the steam reforming process, carbonaceous material is placed in a steam reforming kiln, which usually comprises a drum or kiln that is rotatable. Typically, the CM includes a substantial level of moisture. The drum is rotated to agitate the wet CM, while being heated. Heat is typically supplied by natural gas burners, syngas burners or electrical induction heating within the kiln, but external to the rotating drum.
Steam reforming is an endothermic process. However, unlike incineration, which is exothermic, there is no combustion. Rather, the CM, combined with water, is heated while being agitated, causing a reaction that produces a synthesis gas (“syngas”). The syngas consists primarily of hydrogen (H2) and carbon-monoxide (CO).
A key difference between these two thermal processes is in the respective products generated by these processes. In the case of incineration/combustion, the products are primarily oxidized noxious compounds, whereas steam reforming produces largely beneficial syngas fuels with some minor acid and metal vapours typically much easier to clean than oxidized products of combustion.
Typically, the waste being used as the CM input to the steam reforming process comprises mostly hydrogen and carbon, and a small percentage of other elements such as chlorine, fluorine, sulfur, nitrogen, glass and various metals. For example, municipal solid waste (MSW) typically has a carbon/hydrogen/oxygen ratio of about 1/1.7/0.5. MSW also typically includes about 10% by weight of solid inert products.
In a typical prior art steam reforming process, the syngas is produced in a 2-stage process. First, the drum containing the water and CM is heated, typically for 90 minutes at temperatures in the range of 650° C. Then, the solid materials, including metals and char, are extracted from the drum. At this point, about 60-70% of the CM has been steam reformed to produce syngas. The typical process will then “polish” the syngas to convert remaining hydrocarbons to syngas and the pyrolytic char is separated from the remainder of inert inorganics and burned, or the complete mix of char plus other solids is disposed.